<html xmlns="http://www.w3.org/1999/xhtml">
<head></head>

<body onunload="document.getElementById('tbody').appendChild(document.createElementNS('http://www.w3.org/1999/xhtml', 'span'))">
  <iframe/>
  <tbody contenteditable="true" id="tbody">xy</tbody>
</body>

</html>
